1. Field of the Invention
The invention relates to an appliance for gasification of carbon-containing fuel, residual and waste materials.
2. Discussion of the Prior Art
Fuel and waste materials are to be understood as meaning those with or without an ash content, such as brown or hard coals and their cokes, water/coal suspensions, but also oils, tars and slurries, as well as residues or wastes from chemical and wood pulping processes, such as for example black liquor from the Kraft process, as well as solid and liquid fractions from the waste management and recycling industry, such as used oils, PCB-containing oils, plastic and domestic refuse fractions or their processing products, lightweight shredded material from the processing of automotive, cable and electronics scrap, and contaminated aqueous solutions and gases. The invention can be used not only for entrained-flow gasifiers, but also for other gasification systems, such as fixed-bed or fluidized-bed gasifiers or combinations thereof.
The autothermal entrained-flow gasification of solid, liquid and gaseous fuel materials has been known for many years in the field of gas generation. The ratio of fuel to oxygen-containing gasification agents is selected in such a way that, for reasons of quality of the synthesis gas, higher carbon compounds are cleaved completely to form synthesis-gas components, such as CO and H2, and the inorganic constituents are discharged in the form of a molten liquid (J. Carl, P. Fritz, NOELL-KONVERSIONSVERFAHREN [NOELL CONVERSION PROCESS], E F-Verlag für Energie- und Umwelttechnik GmbH, Berlin, 1996, p. 33 and p. 73).
Using various systems which have gained acceptance in the prior art, gasification gas and the molten liquid inorganic fraction, e.g. slag, can be discharged from the reaction chamber of the gasification appliance separately or together (see German reference DE 19718131.7).
Both systems which are provided with a refractory lining or cooled systems have been introduced for internally delimiting the reaction chamber of the gasification system (see German reference DE 4446803 A1).
Gasification systems which are provided with a refractory lining have the advantage of low heat losses and therefore offer an energy-efficient conversion of the fuel materials supplied. However, they can only be used for ash-free fuel materials, since the liquid slag which flows off the inner surface of the reaction chamber during the entrained-flow gasification dissolves the refractory lining and therefore only allows very limited operating times to be achieved before an expensive refit is required.
In order to eliminate this drawback which is encountered with ash-containing fuel materials, cooled systems working on the principle of a diaphragm wall have therefore been provided. The cooling initially results in the formation of a solid layer of slag on the surface facing the reaction chamber, the thickness of which layer increases until the further slag ejected from the gasification chamber runs down this wall in liquid form and flows out of the reaction chamber, for example together with the gasification gas. Such systems are extremely robust and guarantee long operating times. A significant drawback of such systems consists in the fact that up to approx. 5% of the energy introduced is transferred to the cooled screen.
Various fuel and waste materials, such as for example heavy-metal- or light-ash-containing oils, tars or tar-oil solid slurries contain too little ash to form a sufficiently protective layer of slag with cold reactor walls, resulting in additional energy losses, yet on the other hand the ash content is too high to prevent the refractory layer from melting away or being dissolved if reactors with a refractory lining were to be used and to allow sufficiently long operating times to be achieved before a refit is required.
A further drawback is the complicated structure of the reactor wall, which may lead to considerable problems during production and in operation.
For example, the reactor wall of the entrained-flow gasifier shown in J. Carl, P. Fritz: NOELL-KONVERSIONSVERFAHREN [NOELL CONVERSION PROCESS], E F-Verlag für Energie- und Umwelttechnik GmbH, Berlin, 1996, p. 33 and p. 73 comprises an unpressurized water shell, the pressure shell, which is protected against corrosion on the inside by a tar/epoxy resin mixture and is lined with lightweight refractory concrete, and the cooling screen, which, in the same way as a diaphragm wall which is conventionally used in the construction of boilers, comprises cooling tubes which are welded together in a gastight manner, through which water flows, which are pinned and which are coated with a thin layer of SiC. Between the cooling screen and the pressure shell, which is lined with refractory concrete, there is a cooling-screen gap which has to be purged with a dry, oxygen-free gas in order to prevent flow-back and condensation.